Abstract: The mechanism of the interior straight mortise-tenon joint with wooden peg was analyzed. Through the establishment of geometric, balance and physical equations, the moment-rotation theoretical calculation formula of this type of joint was derived. A good agreement between the prediction and test result was observed, which verified the accuracy of the theoretical calculation formula. Furthermore, the influence of the friction coefficient among mortise and tenon, the width of tenon and the initial gap between mortise and tenon on the moment-resisting performance of the joint were discussed. The results showed that the increase of friction coefficient could improve the moment-resisting capacity of the joint, but had little effect on the initial rotational stiffness of the joint. The increase of tenon width could improve both the moment-resisting capacity and the initial rotational stiffness of the joint. With the increase of the initial gap between mortise and tenon, the slip displacement of the joint increases, and the moment-resisting capacity and initial rotational stiffness of the joint decreases.